Do plants have immune cells ?

Flowering plants are also able to recognise and attack invaders, but not so well, and not in the same way. The cell membranes of plant cells have a range of receptor molecules triggered by binding to antigens on the surface of invaders. The majority of these receptors are specific to proteins, short chain polysaccharides and chitin on the surface of bacterial and fungal cells.

When receptors on the surface of plant cells detect a matching molecule it triggers a response within the cell, and to some extent the rest of the plant and even neighbouring plants as well. The mechanisms for this and nature of the response is an ongoing area of research showing that plants have a surprising degree of sophistication and complexity.

Defence responses at the cell surface trigger the activation of genes within the cell and rapid production of a variety of chemicals to strengthen the cell wall and to harm invaders eating the cell contents. There’s a resource cost in producing these defence chemicals but their effects can also kill the infected area of the plant as well as the invader.

Some of the chemicals produced in response to invaders can also travel along intercellular channels within the plant to trigger a defence response in neighbouring cells as well. In some cases the signalling molecules released in this way are also known to be released into the air surrounding the plant. These airborne molecules can trigger defence responses in neighbouring plants but they have also been known to work as attractants for animals that will attack the original invader.

Whilst plants have the ability to boost defences in one part of a plant in response to attacks in a different part of the plant there are some profound and fundamental differences with our immune cells. One of which is the ability to recognise unknown invaders. We routinely make a range of cells having antigen receptors to cope with potential pathogens we have never experienced. Plants lack this ability. The slow process of mutation and natural selection is the only option for plants using their cell surface receptors to cope with new invaders.